Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque,defaultdict
H,W = map(int,input().split())
s = [["#"]*(W+2)] + [list("#"+input()+"#") for _ in range(H)] + [["#"]*(W+2)]
Q = deque([(1,1,1)])
cnt = 0
for S in s[1:-1]:
    cnt += S.count(".")

while Q:
    x,y,d = Q.popleft()
    s[x][y] = "#"
    if x == H and y == W:
        route = d
        break
    for dx,dy in [(1,0),(-1,0),(0,1),(0,-1)]:
        if s[x+dx][y+dy] == ".":
            Q.append((x+dx,y+dy,d+1))
            s[x+dx][y+dy] = "#"
else:
    print(-1)
    exit()

print(cnt-route)